Thank you Don. Confirmed I have 7.8V at anode of D6 and zero at anode of D7
in RX.
U3 is a TPIC6B595N which is in stock at the usual online electronics
retailers and very inexpensive.
73,
-Josh WU7H
On Thu, May 27, 2021 at 1:33 PM Don Wilhelm wrote:
> Josh,
>
> Your investigation is "spot on" and I would normally recommend replacing
> Front Panel U3. It is possible for it to have one bad input and is
> quite static sensitive.
>
> But first, check that 8R and 8T signal lines are working properly. An
> easy place to check is at the anodes of RF Board D6 and D7.
> The anode of D6 should be near 8 volts during receive and the anode of
> D7 should be close to zero.
> That situation will reverse during transmit.
>
> If you find 8R and 8T are on at the same time, that could be reason for
> the problem.
> If you have a problem with those signal lines, check back on the control
> board at Q1, Q2, Q3 and Q4 to determine where the problem might be.
>
> 73,
> Don W3FPR
>
> On 5/27/2021 4:15 PM, Josh Gibbs wrote:
> > My K2 (SN: 4073) suffered a sudden problem yesterday. I didn't notice
> > anything happening - one minute it was working normally and the next the
> > VFO knob stopped working.
> >
> > All other functions appear to be working normally, but the rotary encoder
> > is disabled.
> >
> > If I ground the V- pin (via 100 ohm resistor) the encoder comes to life
> and
> > functions normally.
> >
> > I have verified good continuity between encoder V- and pin 14 of U3.
> >
> > In the manual it says that the MCU can disable the encoder under certain
> > operating conditions. What might those conditions be? One thought I have
> is
> > that the MCU is disabling it for some reason.
> >
> > My current plan is to try replacing U3. All other functions of U3 appear
> to
> > be working.
> >
> > Any troubleshooting advice would be appreciated. Thanks for reading.
> >
> >
>
>
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